1. Field of the Invention
The invention is based on a piezoelectric actuator module, in particular for an injector in the high-pressure portion of an injection system having the “common rail” type of injection system in a motor vehicle and on a method for installing an actuator module.
2. Description of the Prior Art
One actuator module known in the industry can be used in particular in conjunction with common rail injection systems for Diesel engines. The piezoelectric actuator module is assigned a valvelike valve control module and is used to actuate a valve closing member of the valve control module. By means of the valve control module, a nozzle needle of a nozzle module of the injection valve is actuatable in turn. The nozzle needle cooperates with at least one injection opening leading to a combustion chamber of the engine.
The piezoelectric actuator module typically includes an actuator foot, which is braced on a housing of the injection valve; a piezoelectric component, which when an electrical voltage is applied undergoes elongation; and an actuator head, by way of which the elongation of the piezoelectric component is transmitted to a so-called adjusting piston in such a way that this piston is displaced axially. The adjusting piston, via a hydraulic coupler embodied as a hydraulic chamber, cooperates with a so-called actuating piston, which in turn communicates with the valve closing member. A construction of this kind is also described in German Patent Disclosure DE 199 46 831.
German Patent Disclosure DE 100 43 626 shows a piezoelectric actuator module which is surrounded by an axially extending bush that serves to protect the piezoelectric component against dirt and fuel as well as against damage in the installation process. In the region of the actuator head, the piezoelectric actuator module is sealed by means of a bellows, which on the one hand permits an actuator stroke to occur and on the other can compensate for a negative coefficient of thermal expansion on the part of the piezoelectric component. However, bellows have the disadvantages of requiring a relatively large amount of space and of being cost-intensive components.